Livestock is housed in buildings that need to be ventilated, either naturally or through the use of power equipment. Typically, air is exhausted from power ventilated livestock facilities by an appropriate number of 24 to 60 inch, high volume, electrically powered and controlled fans. This provides the appropriate air exchange rate for the animals housed inside the facility in accordance with environmental conditions present. In general, cooler conditions warrant low or minimum ventilation, just to keep air freshened, while warmer weather warrants a much higher ventilation rate to keep animals cool and comfortable. Power ventilation allows air to be pulled in one end or side opening of a building and through the living area of the animals, to be exhausted by the fans at the other end. This creates the air circulation needed.
Odor is inherent in this production system. Odor is generated from the animals, anaerobic degradation and volatilization of manure and urine, and from other sources present. Dust is also produced from sluffed animal dander and movement of feed. Research has shown that dust molecules attract and hold odor molecules such as ammonia, hydrogen sulfide and a wide range of volatile organic compounds.
This system of ventilation effectively removes dust and odors from the living space of animals, creating a better environment within. However air laden with dust and odor is discharged directly to the atmosphere at the fan end of the facility. This often causes a concentrated and objectionable odor plume downwind from these facilities.
The invention pertains to a livestock facility exhaust system to remove a majority of the dust and other such odorous airborne particulate material from air exhausted by power ventilation equipment from a livestock confinement building and without a significant increase in static pressure within the ventilation system.
It has been theorized that up to 90% of odor molecules exiting livestock production facilities are attached to airborne dust particles. Upon removal of a majority of this airborne material with the disclosed invention, odor release to the atmosphere is significantly reduced with less likelihood that downwind receptors will detect offensive odor.
The purpose of the invention is to substantially reduce the dust and odor discharge from livestock facilities employing power ventilation (as opposed to natural ventilation). This is accomplished by a free standing enclosure of high strength woven synthetic material supported by a hoop structure around the exhaust end of the containment building of the livestock facility. Exhausted air enters the enclosure and is temporarily contained therein. Air circulates around impaction surfaces in the enclosure that promote precipitation of airborne particulates from the air stream. A discharge opening is located at or near the top of the enclosure. Exhaust air rid of most of the airborne particulates moves upward and out through the opening. The enclosure also serves to deflect outside wind from the fan orifices which helps to maintain fan performance.
This structure presents numerous opportunities for removing dust from exhaust air. Dust particles are xe2x80x9cscrubbedxe2x80x9d from exhaust air by impaction, redirection and vortex forces created by the design of the enclosure and strategically placed impaction surfaces and material.
The free standing enclosure structure can be as wide as the fan wall itself. It typically extends out approximately 14 feet from the building and 10 feet from the fans, and is typically about 7 to 12 feet high at its highest point near the building. The sides of the enclosure extend to the building exterior wall. The bottom perimeter of the structure is enclosed with a flap that lies on the ground and is covered with gravel.
The enclosure defines a chamber that serves as a collection and impaction area. Exhausted air moves from the fan orifice to an area of lower pressure inside of the enclosure. The air slows in this area as it impacts various permeable surfaces, without causing a static pressure increase and subsequent reduction in fan efficiency. The air, once impacting the inner surfaces of the enclosure, is generally directed toward the ground where it tends to stall in the area furthest from the fan in the enclosure. Many dust particles will fall out of suspension at this point. The air stream, following a path of least resistance (and lowest pressure), reverses direction and exits out the opening in the top of the enclosure. Part of the air stream passes through the porous enclosure wall and dust is trapped by the fabric. Periodic rain events clean the fabric of excess dust. A disposable ground mat with dust retention characteristics can be placed on the floor of the structure to allow for the collection, storage and removal of accumulated dust as needed (likely once annually).
At times a xe2x80x9cVenturixe2x80x9d effect is created when the ambient wind sweeps over the discharge opening of the enclosure with sufficient speed to create a pressure differential. During such occurrences, air will actually be drawn out of the enclosure.